How can one protect against password hackers that use sniffers like l0pht?

Nowadays, NT administrators face a tough task in ensuring network security,
because of password sniffers such as l0pht, which can sniff an NT password
easily. To solve this, one can use a network sniffer that can detect such
password sniffers. The network sniffer could log a user running a password
sniffer and also issue an alert. An example of such a network sniffer is
LANguard:

The user password never leaves the local machine with Win2000 using Kerberos
security. It is never exposed to the network so it should not be able to be
sniffed.